


I Know What You Did

by shootingstarcipher



Category: Gravity Falls
Genre: Angst, Dark, M/M, Mental Instability, Psychosis, Romance
Language: English
Status: In-Progress
Published: 2016-07-11
Updated: 2016-07-15
Packaged: 2018-07-22 23:16:35
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,562
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7457536
Author URL: https://archiveofourown.org/users/shootingstarcipher/pseuds/shootingstarcipher
Summary: <blockquote class="userstuff">
              <p>The three things in the world Dipper hates are the three things Bill loves. Destruction, chaos, and forgetting. But the one thing Bill can’t forget is the one thing Dipper wants to forget most and he almost succeeds… until a certain demon invades his mind and drags it out of the past for them both to stare at.</p>
            </blockquote>





	1. Past Mistakes

She was following them again, just as she often was. He could see her from where he was sitting on the bus and so could Mabel, once he pointed her out to her. He twisted round and caught her eye before tugging on the sleeve of his twin sister’s pink sweater and gesturing to the woman behind them. He always seemed to be the one to notice her first. It was never Mabel. And he was always much shyer around her than his sister was, who quite often spoke to her.

On this particular occasion, she asked why she was still following them. It wasn’t like they didn’t want her to come with them; it was just somewhat disturbing for the both of them, Dipper in particular (not that Mabel seemed to realise her brother’s distress). The woman behind them didn’t reply. She never did, so it wasn’t especially surprising. Instead of interrogating her, Mabel decided to pay her a compliment in attempt to persuade her into responding and told her she looked nice. Of course, even this wasn’t enough to convince the woman to talk.

She simply stared through them, eventually disturbing Dipper enough to make him turn away and try to force the mental image of her cold, dead eyes out of his mind. Mabel, on the other hand, continued to gaze at her with wonder in her eyes. She leant over the metal bar on the back of her seat and gripped it with both of her hands, tilting her body towards the woman and beamed at her. She did this for most of the bus ride and spoke to her several times during the journey, though both of them knew the woman would never say anything back.

As the bus gradually slowed to a stop, the twins glanced out of the window to see their great uncle Stan - who they commonly referred to as “Grunkle Stan” - waiting for them at the bus stop. They’d been sent to stay with him for the summer in the small, quiet village known as Gravity Falls where he owned a fraudulent roadside attraction he named the Mystery Shack. Their father hadn’t been feeling particularly well of late and it had been decided that in order to give him the opportunity to recover, the two twelve year olds would be cared for by Grunkle Stan over the next few months, not that they were exactly enthused by the idea. The expression on Stan’s face suggested he was just as eager as they were.

When Dipper looked back after he and Mabel had dismounted the bus, he blinked repeatedly in disbelief at the realisation that the woman who had been sitting behind them for almost the entire journey (and who, it is worth noting, had not gotten off the bus before them) was no longer there, as if she had vanished into thin air. Of course, he’d done this many a time, for example, when she appeared behind them on the bus despite having not been seen stepping onto the bus as any other normal passenger had.

She always did this. Appearing and disappearing at will, never saying a word to either of them. It was frustrating and, naturally, distressing. But Mabel seemed happy enough so he didn’t mention it to her, walking alongside her as she followed Grunkle Stan back to the Mystery Shack with their luggage in tow. He knew that if he told her she’d gone again, she’d suddenly be upset and want her to come back. He wasn’t like that. The longer she kept away, the fewer nights he’d have to go without sleep. He didn’t expect to get much sleep that night.

Upon arriving at the Mystery Shack, the twins were introduced to Stan’s two employees: Soos (the handyman) and Wendy (a chronically bored red-headed teenage girl who worked the cashier). Both siblings decided there and then that they would all get along well, even if Soos seemed slightly too keen to impress Grunkle Stan and even if Wendy seemed to be much more interested in getting out of work than anything else. Mabel, more than Dipper, was determined to be friends with them.

Their bedroom (which was actually the attic) was just as decrepit as Dipper had expected. Every surface was speckled with dust and the wooden floorboards looked as if they might break at any moment. Nevertheless, he crossed the floor - without it collapsing underneath him - and set down his suitcase by the bed on the left, claiming it as his own. Perching on the edge of it, he twisted round to gaze out of the triangular window in between the two beds. From it he could see little more than a vast see of mossy green, resulting from the copious number of trees surrounding his uncle’s tourist trap.

Mabel bounded in a second later, nearly crashing into the wall opposite the door after tripping over on some of the clutter that littered the floor. She laughed at herself for falling over and Dipper chuckled along with her, although it would have been clear to anyone else that his heart wasn’t in it. As she lay there, giggling on the floor, her brother began to unpack his belongings. Unlike Mabel, he hadn’t packed everything he’d ever owned - just a few spare changes of clothes, a Rubik’s cube and some books. The books took up most of the room in his case. He never went anywhere without a few of them and, since he’d be away for the entire summer, he’d brought nearly all of them with him.

Dinner was a subject that worried him. He couldn’t imagine Grunkle Stan as a chef and being only twelve years old, neither he nor Mabel were capable of cooking a meal. As it happened, he’d been right not to think of Stan as chef. He took them out to a diner for their evening meal - which Dipper considered an odd place to eat out in the evening - where they ate pancakes served by a grey-haired woman who only ever had one eye open.

While Mabel and Stan talked - about what, Dipper was unsure - he spent his time picking at his food, barely eating anything, and glancing nervously around him every few seconds to make sure his past mistakes weren’t creeping up on him again. He couldn’t get them out of his head. He never could, not since it had happened. It was a miracle he hadn’t been locked away after what he’d done. Sometimes he told himself it wasn’t his fault, that he hadn’t meant to do anything wrong. Other times he told himself he was the personification of evil.

Stan and Mabel fought over the remains of the pancakes still left on Dipper’s plate when he announced that he was ready to go back to the Mystery Shack. It took fifteen minutes for them to decide who was going to finish his meal, and even then no decision was actually made; Stan simply grew impatient and reached over with his fork and took the rest of the pancakes from Dipper’s plate. Mabel grumbled something about not being hungry anyway.

By the time they arrived back at the shack it was already getting late, though you wouldn’t know it judging by the amount of daylight that still remained in the sky. The sun wouldn’t set for hours. That was the price that came with summer. Long days that Dipper found insufferable. And yet he refused to let himself go to bed, knowing full well that if he did manage to fall asleep (which seemed unlikely) he’d wish he hadn’t. As much as he and Mabel both adored being followed and protected by the woman they knew they shouldn’t be able to see at all, he always suffered afterwards. So all three of them stayed downstairs in the living room, Stan in his armchair and the two children sat by his feet, chatting about insignificant things and watching mindless television until late into the night.

When Stan went to bed two hours later, he insisted on the twins going to bed as well. “You have a busy day ahead of you. Don’t think you’ll be getting any breaks tomorrow,” he said, only half-joking about not getting having breaks. Mabel groaned at that but Dipper barely even noticed what he said. He was too busy dragging his feet up the stairs as images of what he was trying to forget most flashed through his brain. His sister was asleep in minutes, but he stayed awake reading until the early hours of the morning, at which point he couldn’t keep his eyes open any longer.

In his dream, he relived the worst mistake he’d ever made.

The images would be there in his mind forever. So would the screams.

But in his dream, the worst mistake he’d ever made was interrupted. A voice he didn’t recognise spoke to him, and appearing before him he saw a beast he definitely did recognise. He couldn’t remember the creature’s name or anything about it except for the fact that he’d drawn it on every piece of paper he’d used up until he was around eight when he grew out of the habit. His teachers were worried about him for the number of drawings he did of the creature, always neatly sketching it on the top left-hand side of every page of his school books.

“Long time no see. Remember me, kid?” it laughed as the horrific images he’d been desperately trying to avoid dissolved into the bright white surroundings, becoming one with the brilliant light he hadn’t realised was there until now. He nodded slowly, unsure of whether he was telling the truth. “Trying hard to forget something, I see,” the one-eyed, golden triangular creature mused, floating slightly closer to him. “I can help you with that.”

Dipper spluttered out a question that even he couldn’t understand. It had meant to sound like “Who are you?” but ended up as a jumbled mash of vowels and consonants that strung together to make an incomprehensible murmur. He remembered the creature’s appearance, but that was all. Not speaking to it! Now it seemed to be frowning at him, if that was possible.

“You know who I am, kid. Bill Cipher, your so-called imaginary friend.” Bill said the last two words so sarcastically it irritated him, though hearing him say the words did at least make him start to remember more. “Anyway, seeing as you seem to have forgotten, allow me to re-introduce myself. I’m your old friend... and I’m a demon.”

“Then why would I want your help?” Dipper almost shouted, but he managed to calm himself and said it in a slightly raised voice instead.

Bill ignored the question entirely. “Listen, kid, you have no idea how lucky you that someone as powerful as me has taken a liking to you.” He floated away from him as he spoke, towards a golden statue of himself that had suddenly manifested across the white, wall-less surroundings. “You should really be a bit more grateful. If it wasn’t for me you wouldn’t even be here.” Dipper wasn’t sure what he meant by that, but he knew he probably didn’t want to find out.

He said he’d think about it. He wasn’t sure if he was lying or not. Bill drifted back over to him, clicked his fingers, and was gone. For a few seconds, his mischievous laughter lingered in the air, echoing off the imaginary walls. Then Dipper woke up screaming, Bill’s final words to him repeating over and over again in his mind.

“I know what you did.”


	2. Reign of Terror

He couldn’t have known. Dipper barely knew. Of course, he knew the basics - the consequences his actions had resulted in - but he was completely oblivious to the details; he may have known what the consequences of his of his actions were, but he had no idea what his actions had been in the first place. If even he was unaware of exactly what he’d done and he was the one who had committed the terrible act, then how on earth could this demon - Bill Cipher - know what he’d done? It just didn’t make sense. Then again, nothing about Bill seemed to make any sense.

Mabel wasn’t in her bed when he awoke so she didn’t hear him screaming. She had ventured downstairs in the middle of the night, into the kitchen to get herself a glass of water. Realising she was gone, Dipper initially panicked, immediately fearing the worst, but soon snapped himself out of it and got up to start looking for her. She’s probably just gone downstairs, he told himself in attempt to calm himself down. She’s always restless, even at night, so she’s gone for a wander. That’s all.

He found her quickly. They bumped into each other on the stairs - she was on her way up and he was on his way down. The glass in her hand her ended up getting knocked as the two of them collided with each other, spilling its contents onto both of them (though thankfully she managed to keep her grip on it so as not to drop it). He gasped when the cold water hit him and if he hadn’t been so relieved to find his sister safe he might have snapped at her. He did, however, tell her to be more careful in future, though she argued back that it was his fault and turned around to walk in the direction she’d come from, grumbling about having to go back to get another glass of water under her breath.

Now that he knew for definite she was safe, Dipper returned to his own bed but instead of going back to sleep, he lay awake in bed, thinking everything through. He couldn’t get the demon’s words out of his mind: “I know what you did.” No he didn’t. That was absurd. But if he didn’t know, then why did he say he did?

Another thing he couldn’t get out of his mind was the image of that woman’s face. He had no clue who she was, except that she was one who had suffered the consequences of his horrific deed. He was sorry, whoever she was. She probably had children. She was probably married. Just thinking about the woman’s identity was enough to shove him into a deep depression from which he expected to never manage to climb out of, but it hit him then that someone - or something - could help him.

Bill Cipher.

He made up his mind that if things continued and got progressively worse, he would have no option but to accept Bill’s offer of help. But what did Bill want in return? And would the offer still stand by the time he got round to accepting it?

Before he had the chance to figure out the answer for himself, Mabel returned to the attic empty handed (having drunk the replenished glass of water downstairs already so her brother couldn’t spill it again) and slipped back into her own bed, interrupting Dipper’s thoughts in the process. She didn’t seem particularly tired either.

“You’ve been quiet today,” she commented, quickly adding “or yesterday” when it dawned on her that it was early in the morning. The night clearly wasn’t over just yet, according the dark colour of the sky outside the attic window - it was a deep, velvety shade of blue, indicating the transition from night to early morning. “You’re always quiet when she’s around,” Mabel continued, using the word “she” to refer to the strange woman who often followed them as they always did. “And when she leaves.”

Dipper didn’t have anything to say to that. He wished she’d stop talking, or at least talk about something else. Like Bill. Mabel had always been the one he spoke to about things he wasn’t comfortable mentioning to anyone else, and a dream demon who apparently used to be his “imaginary friend” (as Bill had put it) seemed like the perfect example to show just how close they were. Or used to be. Every day since the incident, he’d grown quieter. This was the first time Mabel had brought it up.

“Do you… Do you remember someone called Bill?” he asked tentatively, well aware that he was avoiding responding to her mention of his silence completely. She shook her head and mumbled that she had no idea who he was talking about, but not before taking a moment to ponder the question. So Dipper decided to try a different tactic. Taking a notepad and pencil from the pocket of his jacket, he sketched a triangle with arms and legs, a top hat and bow tie and one single eye in the middle of the page. Once he was finished, he held it up and showed it to her.

The drawing, she recognised. “Oh, that’s who you meant,” she gasped as her eyes lit up in a moment of revelation. “Or what you meant. You used to draw it all the time! But… why are you bringing that up now?”

“His name is Bill. He’s…” Dipper trailed off. Something had caught his eye. A shadow that seemed to be moving on its own, in the corner of the room, even though that was impossible. Shadows didn’t move on their own. They couldn’t. Regardless of whether what he saw was possible or not, whether it was real or not, it did at least by him time to consider what he was doing. And once he’d thought about it - really thought about it - he decided he was being ridiculous. He couldn’t tell Mabel. He couldn’t tell anyone. She wouldn’t believe him; she’d think he’d gone mad. Maybe he had. But if he was going to accept Bill’s help, he couldn’t have anyone trying to stop him.

He shook his head, muttering a barely audible “never mind” under his breath. Then he lay down and rolled over, facing away from her. Mabel asked him what the matter was and he ignored her, pretending to be asleep. She stopped trying to get his attention after a few minutes.

He wasn’t sure precisely when he slipped out of consciousness, but at some point during the next ten minutes or so the walls of reality began to melt away until they’d disintegrated entirely and all that was left was a river of deep crimson which he was wading through. By this point he was sure he was dreaming. The demon didn’t need to appear (as he did a while later) for him to determine that.

Whatever he was walking on - the river was much too murky for him to see into it - was soft but it didn’t feel like sand, which was what he’d been expecting. It was spongey and stretchy, and he could pull it up with his bare feet if he latched onto it with his toes. A metallic, salty scent hung in the air. I wonder what that could be, he grumbled to himself sarcastically. There was no doubt in his mind what the stench was. It was too familiar not to recognise. Blood. This, of course, led him to stare down at the body of red liquid he was pushing his way through and halt his movements.

The air was hot and heavy. He could barely see up to two feet in front of him because of a dark, grey mist. The sky behind it was pitch black, but his surrounding were lit by a series of golden stars which were, unfortunately, few and far between. He paused to wonder whose blood he was standing in. It can’t have belonged to only one person. The body of liquid was deep enough to reach above his knees. He swivelled round but in no direction could he see an end to the bloody reservoir, though that may have been the fault of the mist. His clothes were soaked but that didn’t matter. What mattered was that got out of there.

For a moment or so he stood and simply willed himself to wake up. Seeing as he was aware that none of it was real and it was all just a dream, it didn’t seem unlikely that he could wake himself up by telling himself to. It did, however, prove too difficult for him. Perhaps because his mind was busy working away at other things. He couldn’t concentrate fully on breaking away from the dream, not when he had so many other things to focus on, whether he did that consciously or not.

After realising his initial plan had failed, he carried on wading through the thick body of blood, making sure to keep his hands away from the liquid. It was cold against his skin and every so often he shivered, wrapping his arms around his body, and not always because of the cold. Not long after he’d started moving again, he came to a grassy, pastel blue river bank and clambered out of the reservoir, glad to finally be able to turn his back on the enormous body of blood.

The mist cleared, revealing a vast stretch of the same blue grass that lined the riverbank. He blinked a few times before looking up. The darkness suddenly seemed to subside, having been invaded by a brilliant flash of bright light. Gazing up at the sky above him, he found definitive proof that he was in fact dreaming, as if wading through blood hadn’t been enough. In front of him, the sky was pink and a golden sun loomed above, nearly blinding him. And yet, behind him - above the pool of blood he’d just escaped from - was the same black expanse of sky littered with the same golden stars he’d seen before.

He carried on walking. What else was there for him to do? He carried on walking in a straight line ahead of him, intending to stop if ever he saw something new or unusual. Time went by - though how much, he wasn’t sure - and nothing changed. It was as if he was staying in exactly the same position in spite of his movements. The surroundings weren’t moving or changing and his legs were beginning to grow tired even though he was asleep. The blood on his clothes was dry by now, the heat of the sun having soaked up the moisture.

Company was what he wanted most. Normally he was irritated by people hanging around him - sometimes even by Mabel, as there was such a thing as too much of a good thing - but this time, having been alone for the entirety of the dream, he longed for companionship. Even if it was someone he didn’t usually enjoy being around. Even if it was Bill Cipher himself.

He shouldn’t have had that thought. In that moment, he inadvertently invited the demon to invade his mind and disturb the peace he was starting to find within the dream.  
“Enjoying the scenery?”

Dipper scowled when he heard the familiar voice and made a point of staring at the ground, though he had to admit that now he was out of the reservoir (and as long as he kept his gaze away from his blood-caked clothes) it really was beautiful. And now Bill was ruining it.

“Oh, don’t be like that,” the demon continued when he didn’t receive an answer. “I know you like it here. Besides, you thought it yourself: you want me here. Or did you forget that?” Dipper looked up and glared at him, but that only made the demon laugh. “Just kidding!” he exclaimed, suddenly swooping closer to him, making him jump back in surprise. “I’d know if you forgot, and anyway… you can’t forget. You can’t forget something, can you?”

If looks could kill, Bill would have been dead on the spot. But they couldn’t - at least, they couldn’t kill demons.

If he hadn’t been so stressed out, Dipper might have said something a bit more polite than he did, such as “I would appreciate it if you’d abscond from my dream” or “would you mind returning another time?” but instead what he actually did was snap at him to “get the hell out.” Bill didn’t look impressed and tapped his foot impatiently on the empty air, tutting at him and commenting on his grouchiness. Apparently he was much more fun when he was younger, back when the demon was his supposed imaginary friend (though Dipper couldn’t imagine himself being friends with him).

He didn’t say anything for a long time. He was expecting Bill to keep speaking to him but when only silence filled the air, he simply started walking forwards again. The demon followed after him, always staying behind him with his limbs dangling off his triangular body at unnatural angles, and this time the setting changed.

The pink sky turned to purple and the golden sun completely vanished, replaced by a glowing silver moon. Behind him, the purple spread across to the black patch of sky, devouring it along with the stars that had once adorned it as it slithered across. The red reservoir disappeared as well, swallowed up by the scarlet grass that had once been blue. Ahead of the two of them - the human and his demon companion - a colossal willow tree suddenly sprung up from the ground and it too was of unnatural colours; its bark was bronze and its leaves were gold and silver.

When Dipper reached the tree, he paused for a rest and sat on the ground, leaning his back against its oddly metallic trunk. Bill stopped when he did but continued to hover in the air instead of sitting down with him (he did, however, alter his position so that he was sitting in with his legs crossed though he was still lingering above the ground).

“Hear me out, kid,” the demon started and Dipper rolled his eyes at the familiar nickname immediately. “I know you’ve thought about what I said earlier. It’s only been a few hours and I can tell you’re getting desperate. I’m doing this to help you, kid, not because I want you to help me. I’m doing it because I like you. We’re friends, after all.”

“Don’t know what gave you that idea,” Dipper mumbled, raising his head to look the demon in the eye.

“All you have to do is agree to join me. In return I’ll make sure you forget all about that nasty business with…” He lowered his voice. “You know who.” Dipper wondered exactly what he’d been joining him with if he did agree and Bill answered him almost instantly. “My reign of terror, naturally.” Dipper’s eyes widened. He’d said it so casually, as if it were the most ordinary request in the world. The demon went on to explain that he’d be given his own servants, his own suite in his castle (he raised his eyebrows at the mention of a castle) and could have anything he wanted as long as he pledged his allegiance to him and his associates. “I’ll even give you the penthouse suite,” Bill added once his explanation was over.

He knew what Dipper’s decision was even before Dipper knew himself. A blue flame appeared in his hand and before the human knew what he was doing, he was already reaching out to shake it.


End file.
